Fuente: WIPO "essential oil or extracts" The present invention relates to Zinc Oxide nanoparticles and a method for synthesis of Zinc Oxide nanoparticles using Cymbopogon flexuosus plant essential oil. Zinc Oxide nanoparticles (ZnO NPs) characterized in having hexagonal wurtzite crystallite structure, wherein the crystalline size is in the range of 5 - 15 nm. The method comprises preparing essential oil extract of Cymbopogon flexuosus plant; preparing 0.5 M aqueous solution of zinc nitrate by dissolving 4.71 gm of zinc nitrate in 50 ml of triple distilled water, under stirring till the solution becomes clear; adding 7 ml of Cymbopogon flexuosus plant essential oil extract to the aqueous solution of zinc nitrate under continuous stirring on a hot plate magnetic stirrer till the formation of a colloidal white color suspension which further changes into greyish color; maintaining pH 8 using 1 - 3 ml of 0.5 - 1.5 molar NaOH; incubating it undisturbed for 20 - 30 hours at room temperature; separating the nanoparticles by centrifuging the precipitates obtained in step (v); washing nanoparticles four times with tripled distilled water and collecting the Zinc Oxide nanoparticles; and drying the nanoparticles in a hot air oven at 40°C for 13 hours., which possess good antimicrobial and antifungal activity against the numerous pathogenic bacteria and fungus.